1. Field of the Invention
The present invention relates to a power transmission, and more particularly, to a power transmission suitable for a drive mechanism of a compressor used in an air conditioning system for vehicles.
2. Description of Related Art
In a known external signal controlled-type compressor used in an air conditioning system for vehicles such as the compressor shown in Japanese Patent Application No. JP-A-6-34684, the compressor's displacement is controlled by an external signal, and the compressor is connected directly to and driven by an engine. In the known external signal controlled-type compressor, when the air conditioning system is not in operation, the engine drive the compressor at a minimum displacement. Nevertheless, because the compressor is in operation and the engine drives a rotating member of the compressor when the a/c system is not in operation, the energy of the driving engine of the vehicle is wasted.